DROUGHT INTENSITY EFFECTS ON GENOTYPIC DIFFERENCES IN TISSUE AFFINITYFOR STRONGLY BOUND WATER

In an effort to define the role of bound water in drought tolerance, r elationships between the leaf segments affinity for water, leaf water status, leaf area (LA) and drought intensity were analyzed, using thre e durum wheat cultivars grown in a growth chamber. Previous studies in dicated that Appulo and Capeiti 8 cultivars are more drought tolerant than Creso. A new simplified analysis of water sorption that consists of measuring the differences in water sorbed (DWS) by the leaf segment s at two temperatures was applied to evaluate the tissue strength of w ater binding. The turgid weight (TW)/dry weight (DW) ratio was also de termined to obtain a rough estimate of bound water. Five different lev els of soil water content (SWC) were obtained by limiting irrigation w ater for 20 days. The TW/DW ratio was not affected by water deficit. L eaf area, water potential (Psi(w)) and relative water content (RWC) de creased with increasing drought intensity, but genotypic differences w ere not observed. At high SWC Creso showed greater DWS values than App ulo and Capeiti 8, whereas at low SWC the latter varieties had greater DWS values than Creso. The drought induced increase in DWS observed i n the more drought tolerant plants was not related to greater leaf wat er content or growth under drought. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.